1. Field of the Invention
The present invention relates to a photoresist material which is to be formed into a photoresist film on a semiconductor substrate. The photoresist film is used in order that a light exposure may be effected through a reticle mask or other sort of a mask indicating a pattern of a desired semiconductor integrated circuit, and a PEB (Post Exposure Bake) treatment is then performed followed by a developing treatment with the use of a developing solution, thereby forming a rectangular resist pattern. Further, this invention relates to an etching method involving the use of the resist pattern consisting of the photoresist material. Moreover, the present invention also relates to a method for manufacturing a semiconductor device.
2. Description of the Related Art
A light exposure technique according to a prior art employs an exposure device using light exposure beams including g light ray (436 nm) and i light ray (365 nm), further employs a novolack resist material. However, according to a higher integration in LSI (Large Scale Integration) device, a lithography technique is required which uses excimer laser (248 nm, 193 nm). The excimer laser are far ultraviolet lights favorable for micro-treatment. Nevertheless, it has been found that a novolack resist material has a large light absorption and a greatly increased photo-sensitivity but has a difficulty in obtaining a proper resist shape when the novolack resist material is used.
In order to solve the problem, a chemically amplified resist material has been suggested. The chemically amplified resist material will vary in its dessolving selectivity in a resin by virtue of a sensitization reaction of an acid catalyst of an acid generated from a photo-acid generating agent so that a higher photo-sensitivity can be permitted.
Japanese Unexamined Patent Publication Nos. 4-314055 and 6-67413 (hereinafter referred to as prior arts 1 and 2, respectively), have disclosed some examples in which p-hydroxy styrene resin is used as a resin, while a photo-acid generating agent containing a trifluoromethane sulfonic acid ester is used as a photo-acid generating agent. However, in both of the prior arts 1 and 2, since the trifluoromethane sulfonic acid has a relatively long diffusion length, a problem may occurs in using such photo-acid generating agent in a logical device. The problem is that a sparse pattern, rather than a dense pattern, will become narrow in pattern size.
Further, Japanese Unexamined Patent Publication No.5-216234 (hereinafter referred to as prior art 3) has disclosed an example in which p-hydroxy styrene resin is used as a resin, while a naphthoquinone diazido sulfonic acid ester and a further photo-acid generating agent are used as photo-acid generating agents. However, in the prior art 3, the naphthoquinone diazido sulfonic acid ester tends to absorb too much excimer laser (248 nm, 193 nm), resulting in a problem that a resist pattern will become an inverted taper pattern, hence, to cause a deterioration in the resist pattern. Moreover, due to a photo-acid generating agent which produces an acid having a relatively short diffusion length, the irregularities on pattern side walls will become undesirably remarkable.
Therefore, when manufacturing a semiconductor device, particularly in making a logical device, it is important to eliminate resist pattern size differences possibly caused due to different pattern densities.